The present invention relates to a device for measuring moisture, and more specifically to a device for measuring moisture in which the measurement is not affected by the arrangement of the device.
Devices for measuring moisture are known, where a sensor unit having a moisture-sensitive sensor element is mounted on a flat carrier element. The carrier element can be, for example, a circuit board or a wafer. In this case, the required electrical contacts between electrical components mounted on the circuit board, for generating and processing signals, and the sensor unit or the actual moisture-sensitive sensor element, can be provided by bonding wires and corresponding soldered connections.
Alternatively, the contact can also be carried out via connection wires at the sensor unit, which are inserted into suitable contact bores on the carrier element side, and are soldered on the other side to the circuit board. However, from a standpoint of production engineering, use of contact elements of this kind requires substantial expense, which is especially perceived as being negative in the case of mass production. The automated fitting of circuit boards with sensor units of this kind for measuring moisture is difficult or even impossible using these types of contacts.
From WO 98/27411, a locally selective system is known, where, for example, a sensor in the form of a moisture sensor is configured with its moisture-sensitive sensor surface above the recess of a suitable carrier substrate. Flip-chip technology is used for the electrical contacting of the sensor element. However, this device can have the drawback of measured moisture values being invalidated when certain carrier substrate materials are used.
The present invention is a device for measuring moisture, which renders possible a substantially automated manufacture of such devices. The device requires a simplest possible electrical contacting of the components used. In addition, with the present invention, the measured moisture values are not invalidated by the design of the device.
The systems according to the present invention now permit the automatic fitting of circuit boards, wafers, or other carrier elements with moisture-sensitive sensor units. The sensor units can be, for example, SMDs (surface mounted devices). In this case, the sensor units are placed in an automated fashion, by SMD automatic insertion equipment, at the designated positions of the carrier elements designed in accordance with the present invention, secured in place, and electrically contacted. The complete or simultaneous contacting of the sensor unit can be achieved, for example, by hard-soldering, or it can also be achieved by fastening with conductive gel. In comparison to the conventional method of contacting and fitting, the result is a clear reduction in the required process steps due to the now possible flip-chip technology.
In addition, the embodiments of the invention, ensure a trouble-free functioning of the device during the measuring operation, since it is possible to prevent a microclimate from developing in the vicinity of the sensor unit and affecting the measurements.
In one embodiment, the invention is thus a device for measuring moisture, comprising a sensor unit with a moisture-sensitive sensor element, a carrier element defining a recess, wherein the sensor unit is mounted above the recess, and the moisture-sensitive sensor element is oriented in the direction of the recess. The invention also includes first electrical contact regions of the carrier element, second electrical contact regions of the sensor unit, the second electrical contact regions being disposed on the sensor unit facing the carrier element, and a moisture absorption and desorption resistant coating disposed on the carrier element at least in one partial region adjacent to the sensor unit.
Within the scope of the present invention, the most widely varying designs are possible for particular moisture-sensitive sensor units, since the measures described in the following can be adapted to very different circumstances. For example, both capacitive variants, as well as resistive variants of a moisture-measuring device can be implemented in accordance with the present invention.